1. Field of the Invention
The present invention relates generally to an FM demodulating apparatus, and more particularly, to an FM demodulating apparatus of this kind which is suitable for use in demodulation or the like of video signals recorded by, for example, a video tape recorder (hereinafter simply called "VTR") by an FM modulation (frequency modulation).
2. Description of the Prior Art
Conventionally, video signals recorded on a magnetic tape by FM modulation are reproduced from the magnetic tape and FM demodulated, for example, in a VTR (video tape recorder). More specifically, as shown in FIG. 1, a reproduced video signal fed to an input terminal 1 is supplied to an RF signal equalizer (RF equalizer) 2 wherein characteristics of sideband components of the reproduced video signal are equalized so as to be equivalent to the modulation figure of an FM modulation signal upon recording. Then, the output from the RF signal equalizer 2 is supplied to an FM demodulation circuit 3 to be FM demodulated. In that event, as the FM demodulation circuit 3, for example, a pulse counter type FM demodulation circuit is used. The demodulated output from the FM demodulation circuit 3 is delivered to a demodulated video signal output terminal 4.
Such an FM demodulating apparatus demodulates a signal with a wide range of modulation figures so that reproduction of upper sideband components may easily fluctuate due to conditions of reproducing heads and a magnetic tape and so on of a VTR, which causes drop-out of information called reverse phenomenon and accordingly easy generation of noise on the demodulated signal.
Also, employment of a pulse count type FM demodulation circuit as an FM demodulation circuit results in generating a large amount of undesirable components called moire on the demodulated signal in the vicinity of the frequency double the carrier frequency.